Landfill Stability Demonstration

James River Power Station Utility Waste Landfill Greene County, Missouri for City Utilities of Springfield, Missouri

October 16, 2018 Landfill Stability Demonstration

James River Power Station Utility Waste Landfill Greene County, Missouri for City Utilities of Springfield, Missouri

October 16, 2018

3050 South Delaware Avenue Springfield, Missouri 65804 417.831.9700

TABLE OF CONTENTS 1.0 EXECUTIVE SUMMARY ...... 1 2.0 INTRODUCTION ...... 1 3.0 GEOLOGICAL SETTING ...... 2 3.1 Stratigraphy ...... 2 3.1.1 Regional Geologic Setting ...... 2 3.1.2 Bedrock Stratigraphy ...... 2 3.1.3 Local Surficial Geology ...... 3 3.2 Hydrologic Conditions ...... 3 3.2.1 Regional Hydrology ...... 3 3.2.2 Bedrock Aquifers and Confining Units ...... 3 3.2.3 Local Hydrology ...... 4 3.3 Karst Development ...... 4 4.0 LANDFILL SITING, EXPLORATION AND DESIGN ...... 4 5.0 LANDFILL OPERATING HISTORY AND PERFORMANCE ...... 5 6.0 POTENTIAL UNSTABLE AREA MECHANISMS ...... 5 7.0 SITE INVESTIGATION MEANS AND METHODS ...... 6 8.0 GEOPHYSICAL INVESTIGATIONS ...... 6 8.1 ERT Data ...... 7 8.1.2 ERT Data Quality Control ...... 8 8.1.3 Summary of ERT Interpretations ...... 9 8.2 MASW Data ...... 13 8.2.1 MASW Data Quality Control ...... 13 8.2.2 Summary of MASW Interpretations ...... 14 9.0 GEOTECHNICAL INVESTIGATIONS ...... 14 10.0 FINDINGS AND CONCLUSIONS ...... 15 11.0 CERTIFICATION ...... 17 12.0 REFERENCES ...... 18

LIST OF FIGURES Figure 1. Site Location Map Figure 2. Site Diagram Figure 3. Stratigraphic Column Figure 4. Surface Geology Map Figure 5. JRPS Karst Features Figure 6. JRPS Landfill Development Figure 7. ERT Traverse and MASW Sounding Locations Figure 8. Ground Surface Elevations Figure 9. Top of Rock Elevations Figure 10. Soil and CCR Thickness Figure 11. Interpreted Joint Trend Locations Figure 12. Borehole Location Map

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APPENDICES Appendix A. 3D ERT Profiles Appendix B. MASW Data Appendix C. Borehole Data Appendix D. AE Slope Stability Report

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1.0 EXECUTIVE SUMMARY

A Landfill Stability Demonstration was undertaken at the City Utilities of Springfield, MO James River Power Station (JRPS) Utility Waste Landfill (UWL) in accordance with the US Environmental Protection Agency’s (USEPA’s) Coal Combustion Residuals (CCR) Rule, published in the Federal Register on April 17, 2015. The specific requirements for Stability Demonstrations (unstable area demonstrations) are provided in 40 CFR 257.64. The JRPS CCR Landfill is subject to these requirements and is located in a karst area. Karst terrain is one of the considerations to be evaluated in determining whether a CCR landfill is stable.

The original JRPS landfill was permitted and developed in 1985 under MDNR permit no. 707704 and is sited in the floodplain of the James River, directly downstream of Lake Springfield. The landfill design incorporated a two-foot thick compacted clay liner and a perimeter embankment for flood protection. The landfill was subsequently expanded laterally and vertically in 1993 under MDNR permit no. 707705, and incorporated a geomembrane liner and storm water detention pond into the design. The JRPS landfill has operated for over 30 years with no evidence of instability.

The JRPS landfill stability demonstration involved site reconnaissance to assess karst features; geophysical surveys to determine whether cover collapse sinkholes were forming beneath the landfill; drilling and geotechnical testing to determine engineering properties of the fill material and foundation material; drilling, coring and hydrologic testing around the landfill to characterize stratigraphy, hydrology and karst development; and review of existing stability studies which assessed landfill slope stability.

The demonstration found the landfill to be stable. No cover collapse sinkholes were found to be forming within or beneath the landfill. Very few solutional voids were found in the underlying bedrock, and those that were found were generally filled with alluvial sands and gravels. Landfill slopes were found to be stable, both for existing conditions and complete buildout conditions. Total settlement and differential settlement are considered to be insignificant with respect to landfill stability. Sections 8.0 and 9.0 of this report discuss these findings in greater detail.

2.0 INTRODUCTION

On April 17, 2015, the United States Environmental Protection Agency’s (USEPA’s) final Coal Combustion Residuals (CCR) Rule was published in the Federal Register. The CCR Rule establishes five (5) location restrictions for CCR landfills. Four (4) of the location restrictions (placement above the uppermost aquifer, wetlands, fault areas, and seismic impact zones) apply only to new CCR landfills. The fifth, unstable areas, applies to both new and existing CCR landfills. Unstable areas are defined as locations that are susceptible to natural or human-induced events or forces capable of impairing the integrity, including structural components of some or all of the CCR unit that are responsible for preventing releases from the unit. Unstable areas can include poor foundation conditions, areas susceptible to mass movement, and karst terrains.

40 CFR 257.64 requires an owner or operator of an existing CCR landfill to demonstrate by October 17, 2018 that recognized and generally accepted good engineering practices have been incorporated into the design of the CCR landfill to ensure that the integrity of the structural components of the CCR landfill will not be disrupted. Section 257.64 further requires the owner or operator to consider all

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of the following factors, at a minimum, when determining whether an area is unstable: 1) onsite or local soil conditions that may result in significant differential settlement, 2) onsite or local geologic and geomorphological features, and 3) onsite or local human-made features or events (both surface and subsurface).

The JRPS UWL is located in an area of karst terrain. This demonstration details the investigations undertaken to assess the stability of the JRPS UWL with respect to site-specific karst features and forms the basis for certification of the UWL’s stability. The location of JRPS is shown in Figure 1. A diagram of the JRPS UWL is provided as Figure 2.

3.0 GEOLOGICAL SETTING

3.1 Stratigraphy

3.1.1 Regional Geologic Setting The JRPS site is located in the Springfield Plateau Sub-province of the Ozark Plateau Physiographic Province. The bedrock surface of the Springfield Plateau generally consists of thick Mississippian-age limestones and cherty limestones above Ordovician- and Cambrian-aged strata. Bedrock generally dips gently toward the west with minor folding and faulting. Most of the area faults have less than 50 feet of displacement. The predominantly limestone strata in the area has been extensively weathered, and the irregular bedrock surface is hidden below a mantling of cherty clay residuum with thicknesses that vary from a few feet to over 40 feet.

3.1.2 Bedrock Stratigraphy The Springfield Plateau is underlain at depth by Precambrian crystalline basement rock that serves as the lower groundwater confining unit. The Precambrian basement is overlain by the Cambrian-aged Lamotte Sandstone consisting of approximately 150 feet of sandstone. This unit is overlain by around 200 feet of dolomite, the Bonneterre Formation, and 150 feet of shale, the Davis Formation. The Derby-Doerun, Potosi and Eminence Dolomites overlie the Davis Formation and are cumulatively around 500 feet thick. The top of the Eminence Formation marks the top of the Cambrian Period, as well.

The Ordovician-aged Gasconade Formation consisting of 350 feet of dolomite and up to 25 feet of sandstone overlies the Eminence Formation. The overlying Roubidoux Formation consists of around 150 feet of dolomite, dolomitic sandstone, and sandstone. Between 250 and 600 feet of dolomite divided into the Jefferson City and Cotter Formations mark the top of the Ordovician Period below the Springfield Plateau.

In the vicinity of JRPS the Cotter Dolomite is unconformably overlain by around 30 feet of the Mississippian aged Compton Limestone; the Devonian and Silurian Periods being entirely missing from the geologic record. The Compton Limestone is overlain by between 5 and 30 feet of shale and siltstone of the Northview Formation. The Northview Formation is overlain by less than 100 feet of the Pierson Limestone, which is overlain by the Elsey-Reeds Spring Formation, consisting of up to 200 feet of cherty limestone. The Elsey-Reeds Spring Formation is capped by the Burlington-Keokuk Limestone, which forms the bedrock surface across most of the Springfield Plateau and due to the high degree of weathering, may be from 150 to 250 feet thick. A stratigraphic column is provided as Figure 3.

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3.1.3 Local Surficial Geology The JRPS CCR landfill is sited in the floodplain of the James River within a bend directly downstream of Lake Springfield. The site is directly underlain by residual soil and alluvium. The residual soil is weathered from terrace deposits to the north and west of the landfill. The alluvium was deposited by James River and consists of silty-clay sediment with lenses of more granular sand and gravel. The alluvium overlays Burlington-Keokuk Limestone exhibiting an irregular solutional surface. Stratigraphically, the site corresponds with the Burlington-Keokuk/Elsey-Reeds Spring Transition Zone, which is exposed in bluffs along the river and is continuous beneath the valley floor. The Elsey Formation is exposed on valley slopes directly upstream of Lake Springfield, but dips beneath the valley floor in the vicinity of the JRPS landfill and the river valley downstream. Boreholes indicate the top of the Elsey Formation occurs around elevation 1100 feet msl (approximately 30 feet beneath the floodplain surface). The Burlington-Keokuk/Elsey-Reeds Spring Transition Zone is the stratigraphic horizon exhibiting the greatest degree of karst development in the area, as evidenced by the number of springs (Camp Cora Spring, etc.) which discharge near river level along this stretch of the James River. A map depicting surface geology is provided as Figure 4.

3.2 Hydrologic Conditions

3.2.1 Regional Hydrology The Springfield Plateau is underlain by three bedrock aquifers, the St. Francois Aquifer, the Ozark Aquifer, and the Springfield Aquifer (Emmett et al, 1978). Of these, the Ozark Aquifer is the most important groundwater source in the Springfield area. The Ozark Aquifer has an average thickness of approximately 1,200 feet in the Springfield area, thinning to the north and thickening to the south. The Ozark Aquifer is confined and is artesian where pumping hasn’t produced a large cone of depression in the potentiometric surface.

3.2.2 Bedrock Aquifers and Confining Units The Springfield Aquifer in the Springfield area varies between 100 to more than 300 feet thick and encompasses the Burlington-Keokuk Limestone, Elsey-Reeds Spring Formation and Pierson Formation. Groundwater flow primarily occurs along fractures, bedding planes, and voids causing flow velocities to be widely variable across the Springfield Plateau. The Northview Formation and the Compton Limestone form an effective aquitard, restricting migration of groundwater into the underlying Ozark Aquifer. The overall hydraulic conductivity of the aquifer is estimated to be 2.5x10-4 feet per second and the transmissivity ranges from about 1.0x10-2 to 5.0x10-2 square feet per second. The Springfield Aquifer is not used as a drinking water source in Greene County (designated Sensitive Area C) in accordance with Missouri Well Construction Code regulations as outlined in 10 CSR 23-3.

The Ozark Aquifer is the primary aquifer used for groundwater on the Springfield Plateau. It is on average approximately 1,200 feet thick, thinning to the north and thickening to the south of Springfield. The Upper portion of the aquifer consists of the Cotter and Jefferson City Dolomites and is capable of yielding 30 to 70 gallons per minute. The lower portion of the aquifer includes the Roubidoux Formation, Gasconade Dolomite, Eminence Dolomite, and Potosi Dolomite and yields from 100 to 200 gallons of water per minute. Estimates of transmissivity of the Ozark Aquifer in Springfield, Missouri vary from 860 to 4,320 square feet per day and estimates of the horizontal hydraulic conductivity vary from 4.3 to 43 feet per day (Imes, 1989). The Bonneterre Formation and Lamotte Sandstone form the St. Francois deep aquifer with the Davis Formation acting as the confining unit.

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3.2.3 Local Hydrology The Springfield Aquifer is unconfined, allowing surface water to percolate through clay residuum into the bedrock below. The percolation of groundwater is aided by increased secondary porosity of the jointed bedrock below, and solutional widening of those joints. In the vicinity of JRPS, James River is classified as a gaining stream and interacts directly with the Springfield Aquifer. Other stream segments which are topographically higher than James River are classified as losing streams, and serve to recharge the shallow karst system which, in turn, discharges at springs along the James River.

The potentiometric surface beneath the CCR landfill rises and falls with river stage. The direction of groundwater flow is generally toward the river or down valley but can reverse temporarily during flood stage.

3.3 Karst Development Karst features in southwest Missouri include springs, caves, solution-widened joints, cutters and pinnacles, solutional sinkholes, and collapse sinkholes. Solution-widened joints form when slightly acidic groundwater percolates through the existing joints in soluble bedrock, slowly dissolving and widening the joint. Cutters and pinnacles form where tightly-spaced and roughly perpendicular intersecting joint sets are widened by solution, leaving spires of bedrock separated by joints that narrow with depth. A solutional sinkhole is bounded by a definable rim and is generally a circular or oval-shaped depression. Some solutional sinkholes contain an “eye” where groundwater quickly enters subsurface drainage galleries formed by intersecting solution-widened joints. Solutional sinkholes form as the bedrock surface is dissolved by solution, causing the overlying soil to subside and form a surface depression. Collapse sinkholes form when a void in the subsurface soil propagates toward the surface until the roof of the soil cavity collapses, forming a relatively steep-sided roughly cylindrical to cone-shaped cavity from the surface to the bedrock below. Collapse sinkholes occur along bedrock joints and are typically triggered by an increase in soil moisture content.

Winoka Spring, directly upstream of Lake Springfield, and Camp Cora Spring, on the opposite side of James River across from the JRPS UWL, are master springs that discharge from the Burlington- Keokuk/Elsey-Reeds Spring Transition Zone. Dye tracing has confirmed that sinkhole areas to the east drain to these master springs. These, and other dye traces in the area, show the karst system to drain to the west-southwest; generally down-dip with respect to bedding planes developed within the stratigraphic units. There are a few isolated sinkholes on the upland area to the northwest of the UWL, but no springs at the base of the bluff adjacent to the UWL. These sinkholes likely drain to springs farther to the west- southwest. The next master spring that surfaces in the James River valley downstream of JRPS is Patterson Spring, which is located approximately 4 miles down valley. Springs that are mapped on the left bank of the James River, surfacing directly upstream of the UWL, are likely the result of leakage from Lake Springfield. There is no indication from the data that any karst conduits exist beneath the UWL.

Karst features in the vicinity of JRPS are shown in Figure 5.

4.0 LANDFILL SITING, EXPLORATION AND DESIGN

The JRPS CCR landfill was developed in two phases, as shown in Figure 6. The original 17-acre landfill was permitted and developed in 1985 in accordance with MDNR requirements under permit number 707704. The western boundary of the original landfill corresponded with the City Utilities property line at that time. The eastern boundary was configured so the landfill would not infringe upon the US Army Corp of Engineers

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designated floodway for the James River. The original landfill incorporated a perimeter flood protection berm constructed to a minimum elevation of 1,136 feet (approximately 2 feet above the 25-year flood elevation). A pre-existing sanitary sewer trends north to south beneath the landfill site. In conjunction with landfill development, manholes were raised to accommodate the landfill fill material and granular bedding around the sanitary sewer pipe was grouted and sealed at both ends of the landfill site.

In 1993, MDNR issued permit number 707705 for a 26-acre expansion of the original landfill onto land newly acquired by City Utilities. The landfill expansion included raising the surface of the existing landfill by approximately 4 feet. In addition, the landfill was expanded to the west and southwest, providing an additional 17 acres of storage area. The expansion was lined with 2 feet of compacted clay and a 60-mil thick geomembrane and incorporated a leachate collection system consisting of drainage media located between the liner and CCR and a collection pond. The collection pond was located at the south end of the original landfill and was also lined with a geomembrane and compacted clay (Burns & McDonnell, August 1994). The geomembrane liner was also placed over the top of the original landfill area and incorporated a “window” that is nominally 130 feet x 180 feet in dimension to allow water beneath the liner to migrate to the stormwater detention pond.

5.0 LANDFILL OPERATING HISTORY AND PERFORMANCE

The JRPS CCR landfill operated continuously from 1985 until 2017, when the power station ceased using coal as a fuel. During operation, CCR materials were placed and compacted in the landfill with periodic outer embankment build-ups, as necessary. Conditioned (wetted) fly ash from the dry fly ash collection system was transported daily to the inner surface of the landfill for placement and compaction. Periodically dewatered fly and bottom ash from the surface impoundments on the east side of the James River were transported to the inner working face of the landfill for use in outer embankment construction. As ash filling progressed, the sidewalls and retaining berms were extended upwards at a 3:1 slope, such that the elevation of the outboard clay bank was always higher than the ash working surface.

The JRPS CCR landfill operated continuously since development with no indication of instability. The landfill was designed to promote stormwater runoff, minimize changes in moisture content within the foundation materials, and provide for effective flood protection. These design elements constitute recognized and generally accepted good engineering practices to ensure that the integrity of the structural components of the CCR landfill would not be disrupted.

6.0 POTENTIAL UNSTABLE AREA MECHANISMS

The one karst landform which has potential to compromise the integrity of CCR unit components is the cover collapse sinkhole. Cover collapse sinkholes originate at the soil-bedrock interface when soil is eroded into underlying bedrock solution cavities. The resulting soil void can propagate upward until it manifests as a surface collapse or, in the case of CCR landfills, until it undermines the structural support of landfill components such as liners and leachate collection systems. The mechanics of cover collapse sinkhole formation are well understood. Formation of cover collapse sinkholes is typically initiated by changes in soil moisture content. As soil moisture content increases, the unit weight of the soil increases and soil strength decreases. Cover collapse sinkholes can form in areas with no surface expression of karst but do require

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the existence of a solution-widened bedrock joint which is filled with residual soil that supports the overlying soil and a solution cavity beneath the residual soil to receive the eroded material.

7.0 SITE INVESTIGATION MEANS AND METHODS

A Landfill Stability Demonstration in a karst setting must assess whether a cover collapse sinkhole has formed, or is forming, beneath the landfill. A cover collapse sinkhole would be manifest as a vertical void extending from solution cavities within the underlying limestone bedrock upward toward the landfill material.

GeoEngineers has extensive experience investigating cover collapse sinkholes in karst areas and has found that Electrical Resistivity Tomography (ERT) coupled with Multichannel Analysis of Surface Waves (MASW) is a very effective means to identify and characterize these features. ERT is a non-intrusive imaging method designed to measure spatial variations (2-D or 3-D) in the electrical resistivity of soil and rock. The ERT tool also measures spatial variations in the electrical resistivity of CCR. Cover collapse sinkholes would be manifest as vertical zones of very high electrical resistivity (air-filled voids) extending upward from the bedrock surface. MASW is a non-intrusive acoustic imaging method designed to measure spatial variations (1-D) in the average shear wave velocity of soil and rock. It also measures spatial variations (1-D) in the shear wave velocity of CCR. ERT and MASW surveys were completed at the JTEC landfill.

The geophysical data was complimented by borehole, core hole, and geotechnical data compiled at the site since development of the UWL in 1985. The information from these boreholes was reviewed and compared to corresponding ERT data in order to refine and support the data interpretations.

8.0 GEOPHYSICAL INVESTIGATIONS

Electrical resistivity tomography (ERT) data and multichannel analyses of surface wave (MASW) data were acquired across and in proximity to the JRPS CCR landfill. In total, 136,000 lineal feet of ERT data were acquired along one hundred and thirty-four (134) separate traverses. MASW data were acquired at a total of 39 separate locations.

The ERT data were acquired using an AGI SuperSting system coupled to a dipole-dipole array consisting of 168 electrodes spaced at 5 ft intervals. The intent of imaging the subsurface to depths on the order of 120 ft. A 5-foot electrode spacing was employed to ensure relatively high-resolution (vertical and lateral) ERT data were recorded. A non-standard array of 168 electrodes was employed so that the subsurface could be imaged to depths greater than 120 feet. The west-east oriented traverses ERT traverses were spaced at 20-foot intervals (north-south) so the 2-D data could be processed as a 3-D data set.

The MASW data were acquired using a 24-channel Seistronix engineering seismograph and 4.5 Hz geophones spaced at a 5-foot interval and, in some instances, a 2.5-foot interval as well. The MASW data were acquired using a 24-channel Seistronix engineering seismograph and 4.5 Hz geophones spaced at both 5 ft. intervals with the intent of imaging the subsurface to depths on the order of 100 feet. In areas where interpretable MASW data could not be acquired using a 5 ft. geophone spacing (generally because of the irregular depth to top of rock along the length of the geophone array), a geophone spacing of 2.5 feet was also employed.

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The one hundred and thirty-one (131) W-E oriented ERT traverses are labeled 400-528, 537 and 538 are spaced at 20 foot-intervals (south to north). The ERT data acquired along each of these one hundred and thirty-one (131) traverses were initially processed as a 2-D data set; the initial output of processing was a suite of one hundred and thirty-one (131) 2-D ERT profiles (labeled 400-528, 537 and 538; not shown in this report). The entire suite of 2-D ERT profiles was subsequently reprocessed as a single 3- D data set. This 3-D ERT data set is included in Appendix A as a suite of one hundred and thirty (130) ERT profiles (labeled 400-401 to 537-538; referred to herein as 3-D ERT profiles), each of which was essentially extracted from the processed 3-D ERT data set for visualization and interpretation purposes. The 3-D ERT profile 401-402, for example, is a resistivity image of the subsurface along a “traverse” located mid-way between actual ERT traverses 401 and 402. The 3-D ERT profile 451-452 is a resistivity image of the subsurface along a traverse mid-way between ERT traverses 451 and 452. 3-D ERT profile 480-481 is similarly a resistivity image of the subsurface along a traverse mid-way between ERT traverses 480 and 481.

The three (3) N-S oriented ERT traverses labeled 533, 535, and 536 are spaced at 20 foot-intervals. The ERT data acquired along each of these three (3) traverses were processed as a single 3-D dataset.

The ERT data were acquired at the JRPS landfill with the goal of imaging the subsurface to a depth of approximately 120 feet and providing insight into groundwater seepage/flow patterns below and in proximity to the JRPS landfill. The entire ERT data set is presented in Appendix A of this Report.

MASW (multichannel analyses of surface wave) data were acquired at specific locations along west-east oriented ERT traverses and (mostly) at 200 ft. intervals. Where necessary, MASW data acquisition locations were shifted because of access issues (ponded water, roadways, steep dips, etc.). The MASW data were acquired with the goal of determining the engineering properties of the subsurface to depth of approximately 100 ft. The entire set of interpretable MASW data are presented in Appendix B.

8.1 ERT Data Three contoured maps were generated for the JRPS site based on the interpretation of the acquired 3- D ERT control: 1) JRPS Ground Surface Elevation; 2) JRPS Top of Rock Elevation; and 3) JRPS Combined Soil and CCR Thickness. These three contoured maps are presented as Figures 8, 9 and 10, respectively.

As illustrated by the JRPS Ground Surface Elevation map (Figure 8), the raised perimeter embankment of the CCR storage area is elevated by 40+ feet relative to the natural ground surface and elevated by 5+ feet relative to the central section of the CCR fill. Rain water that falls on the outside slope of the perimeter embankment flows (as stormwater runoff) down the embankment and away from the CCR landfill (as indicated by the blue arrows). Rain water falling on the interior of the perimeter embankment flows toward the stormwater collection manhole tied into the leachate collection system where the detention pond was located prior to the last phase of fill (as indicated by the red arrows). Some stormwater flows from the upper terrace toward the CCR landfill (as indicated by the black arrows) and is diverted around the landfill by the perimeter berm.

In Figure 9, the JRPS Top of Rock Elevation map is presented. This map is consistent with ERT control, MASW control, available borehole control, and general topographic trends. The Top of Rock map shows higher elevations to the northwest, indicating the landfill was constructed immediately to the southeast of a stream-cut terrace. The bedrock surface beneath the CCR landfill is somewhat irregular due to solutional

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weathering of the limestone, but generally slopes from north to south. There is an indication of slightly lower bedrock trend along the upper terrace face, which probably indicates the trend of an ancestral James River stream channel location.

In Figure 10, the JRPS Combined Soil and CCR Thickness map is presented. This map is consistent with ERT control, MASW control, surface elevation, borehole control, and general topographic trends. The map indicates that alluvial deposits within the floodplain generally range from 5 to 20 feet in thickness, areas containing CCR fill to exhibit a combined thickness that generally ranges from 25 to 50 feet, and the combined thickness of materials beneath the perimeter embankment to generally range from 50 feet to 70 feet.

8.1.2 ERT Data Quality Control In order to ensure good to excellent quality ERT data are acquired, the field crews routinely perform contact resistance tests. The contact resistance tests are performed after the metal electrodes (metal stakes) have been inserted into the ground and coupled (via cables) to the recording instrumentation. The contact resistance test is performed prior to data acquisition to ensure all of the metal electrodes are connected properly to the cables (electrically and in proper sequence) and to the ground. If the metal electrodes are not properly connected to the cables or to the ground, anomalously high resistance values are displayed on the instrumentation screen for that specific metal electrode. If anomalously high resistance values are displayed for a specific metal electrode, the field crew physically checks to ensure the metal electrode is properly connected (electrically) to the correct cable. The field crew also wets the ground in the proximity of the metal electrode and increases its insertion depth. In those rare instances (e.g. metal electrode inserted into very dry porous sand) where the contact resistance of a specific metal electrode cannot be reduced to an acceptable level, that electrode is “deadened”.

During ERT data acquisition, calculated apparent resistivity values and their output errors are monitored (viewed on the instrumentation screen) on an ongoing basis. Each calculated apparent resistivity value represents the average of multiple values generated over multiple cycles; a low output error indicates the values that were averaged were very similar. If the output errors are consistently too high or/and if negative resistivity values are present, data acquisition is terminated and the cable connections and metal electrodes are re-checked. In order to minimize potential output errors, the ground in proximity to each metal electrode may be periodically wetted on drier, hotter days.

During data processing, anomalous apparent resistivity data are automatically removed by the processing software. According to the manufacturer of the processing software, as the percentage of removed data increases – overall reliability of the data decreases.

The processing software ultimately generates an output 2-D or 3-D resistivity image for each acquired ERT data set. It also generates an RMS error estimate for each output 2-D or 3-D resistivity image. The RMS error is an indication of the degree of correlation between the field data and the output 2-D or 3-D ERT resistivity profiles. In our study area, excellent quality (in terms of the probable reliability of the output ERT profiles) 2-D or 3-D ERT profiles have RMS errors of less than 4 percent. Good quality ERT profiles (in terms of their probable reliability) have RMS errors of 5 percent to 8 percent. Poorer quality ERT profiles have assigned RMS errors of 8 percent or higher. The RMS error is not necessarily indicative of the quality of the acquired field data. Rather, it is an indication of the reliability of the output 2-D or 3-D ERT resistivity profile.

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8.1.3 Summary of ERT Interpretations An assessment of the suite of 3-D ERT profiles (Appendix A) and the maps presented as Figures 10 and 11, can be used to determine if there is any evidence of formation of cover collapse sinkholes beneath the landfill. The data indicate that rain water that falls on the fly ash deposit follows several potential seepage and or flow pathways:

Pathway 1 and 2: 3-D ERT profile 401-402 is shown below. This 3-D ERT profile images the upper terrace, the lower terrace (on which CCR fill has been placed), and the north-south trending ancestral stream channel located immediately to the west of the CCR landfill. Seepage Pathway 1 depicts surface run off flowing down slope from the upper terrace seeping into the subsurface along or in proximity to the ancestral stream channel. Where the western flank of the CCR landfill abuts the ancestral stream channel, run off from the upper terrace would flow into the western drainage ditch. Some of this water would seep into the soil and underlying rock along mostly vertical pathways. Some water could also flow eastward along the top of rock beneath the CCR landfill. Seepage Pathway 2 depicts water flowing along the bedrock surface from the upper terrace and seeping into the subsurface along or in proximity to the ancestral stream channel. Some of this water would seep into the soil and underlying rock along mostly vertical pathways as depicted below. Some water could also flow eastward along the top of rock beneath the CCR landfill.

Pathway 3: 3-D ERT profile 432-433 is shown below. A visual examination of the profile indicates that the electrical resistivity of the CCR fill (near the structural top of the fill) typically decreases from about 125 ohm-m to approximately 10 ohm-m. This indicates that the shallower CCR material is drier and that the moisture content of the CCR fill generally increases with depth. Some rain water seeps through the grass-covered clay cap and through the underlying CCR material to the clay liner along Pathway 3. Note that several pod-shaped zones of higher electrical resistivity are imaged above elevation 1150 feet. These are interpreted as zones comprised of more porous and permeable CCR material.

Pathway 4: The 3-D ERT profile indicates some of the stormwater runoff from the outboard side of the perimeter embankment seeps into soil and rock near the toe of the embankment along Pathway 4. Most

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of this moisture seeps into the pervasively fractured rock along near-vertical pathways. As shown below, seepage volumes appear to be greater near the toe of the embankment and to decrease with increasing distance from the toe.

Pathway 5: The 3-D ERT profile indicates stormwater seeps into soil and underlying rock as it flows away from the landfill along natural and/or man-made surface drainage pathways (Pathway 5). Seepage patterns indicate seepage pathways through rock are mostly vertical. Seepage volumes appear to be higher where natural or man-made impediments (berms, drainage ditches, etc.) are present.

Pathway 6: 3-D ERT profile 438-439 is shown below. This profile indicates that the moisture that seeps into the CCR material where the HDPE liner has been placed over older CCR fill (shown as a red line), flows down the slope of the liner to the outer edges of the liner. The moisture that flows off the edges of the liner seeps vertically into the CCR fill and underlying soil and rock mostly along near-vertical pathways. The profile also shows the CCR, soil and rock beneath the liner to be relatively dry.

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Pathway 7: 3-D ERT profile 448-449 is shown below. This profile shows some of the moisture that follows seepage Pathways 1, 2, 4 and 6 to flow along or near the top of the pervasively fractured shallow rock beneath the landfill and migrate vertically into the bedrock.

Pathway 8: 3-D ERT profile 480-481 is shown below. This profile shows moisture to seep into the CCR material along Pathway 8 through the designed gap in the liner at the stormwater detention pond. Some of the moisture that follows seepage Pathway 8 could flow along or near the top of the pervasively fractured shallow rock beneath the landfill.

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Pathway 9: 3-D ERT profile 491-492 is shown below. This profile shows two discrete seepage pathways beneath the liner which correspond to liner seams shown on as-built drawings. These seepage pathways are interpreted as small separations in the liner seams. A visual examination of this 3-D ERT profile indicates that some of the moisture seeps into the fly ash flows through two (apparently separated) seams in the liner. Most of this moisture that follows Pathway 9 follows near-vertical pathways into the underlying soil and rock. However, some of the moisture that follows Pathway 9 could flow along or near the top of the pervasively fractured shallow rock beneath the landfill.

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Pathway 10: 3-D ERT profile 526-527 is shown below. This profile lies south of the CCR landfill and illustrates that the sanitary sewer in the vicinity of the CCR landfill can also be imaged by ERT. Moisture seeping into the subsurface can intercept the preferential pathway created by the granular fill around the pipe.

Although these variations in moisture content do exist in and around the CCR landfill, there is no indication of any air-filled voids in the subsurface which would suggest formation of cover collapse sinkholes beneath the CCR landfill.

8.2 MASW Data MASW data were acquired at the JRPS site to provide insight into the engineering properties of the CCR material, soil and rock, and to confirm depth to bedrock for ERT interpretations. Specific objectives included mapping variations in the elevation of top of rock, mapping variations in the rigidity of CCR, mapping variations in the rigidity of soil, mapping variations in the rigidity of rock, and constraining and verifying the interpretation of the ERT data.

8.2.1 MASW Data Quality Control In order to ensure that good to excellent quality MASW data are acquired, the field crews routinely assess each MASW data set in the field. If the initial MASW field data are poor quality, a second MASW data set is acquired using a shorter geophone spacing (2.5 feet as opposed to 5 feet). If the second MASW data set is poor quality, the orientation of the geophone array is rotated by 90 degrees and third and fourth MASW data sets are acquired using 5-foot and 2.5-foot geophone spacings. At approximately 30 percent of the test locations (all where CCR fill was not present), interpretable quality MASW data could not be acquired, presumably because of the weathered nature of shallow rock and variable depth to top of rock along the length of the geophone arrays.

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8.2.2 Summary of MASW Interpretations The depth to top of rock proved to be well-defined on all of the interpretable 1-D MASW shear wave velocity profiles. The shear wave velocity of rock (in the study area and over the depth ranges tested) generally increases significantly with depth (from 1500 ft/s to more than 3500 ft/s), indicating that shallower rock is more weathered than rock at greater depth. This is consistent with the interpretations that moisture following Pathway 7 could flow laterally at or near the top of the pervasively fractured bedrock.

The contact between the CCR material and the underlying soil cannot be mapped on either the ERT data or the 1-D shear-wave velocity profile. However, an assessment of the 1-D MASW shear wave velocity profiles indicate that the velocity of the CCR material and underlying soil increases with depth from lows of about 400 ft/s to highs in excess of 1000 ft/s.

The shear-wave velocity of rock generally increases significantly with depth (from 1500 ft/s to greater than 3500 ft/s), indicating that shallower rock is significantly less intact (more weathered) than rock at greater depth. This is consistent with the interpretations that moisture following Pathway 3 could flow laterally (down dip) at or near the top of the steeply dipping and pervasively fractured bedrock.

The interpreted depths to top of rock on the 1-D MASW shear-wave velocity profiles and the corresponding ERT profiles correlate reasonably well. Differences in depth to top of rock estimates can be attributed to several factors: 1) the MASW data were acquired along 115 foot long geophone arrays oriented close to the continuous ERT profiles (hence the MASW depths represent the average depths to top of rock along the length of a 115 ft-long array); 2) the MASW top of rock is based on the contrasting acoustic properties of soil and rock, whereas the ERT top of rock is based on the contrasting electrical resistivities of soil and rock; and 3) ERT data are higher resolution than MASW data.

The entire suite of interpretable MASW data (including field records, dispersion curves and 1-D shear-wave velocity profiles) are included in Appendix B. Overall, the interpretations of the ERT and MASW data are comparable. While there are variations in shear wave velocity and electrical resistivity data, the data do not indicate that there are any anomalies representative of instability.

9.0 GEOTECHNICAL INVESTIGATIONS

Prior to the first phase of JRPS CCR landfill development, 20 boreholes (borings 101 through 120 in Figure 14) were advanced below and around the initial landfill footprint. These borings are referenced in the 1991 Nuccitelli Landfill Expansion Report, but the original boring logs no longer exist.

From 1989 through 1991, and prior to construction of the second phase of the CCR landfill, Palmerton and Parrish, Inc. under the direction of Saul A. Nuccitelli completed borings numbered 201 through 241 and A through F, and test pits numbered 301 through 317, were completed in and around the landfill expansion footprint. Monitoring wells MW1, MW2, MW2H, MW-3, and MW-4 were also installed around the expanded landfill perimeter. Borings 401 through 403 were completed to characterize the CCR material in the existing landfill. Monitoring wells MW1, MW2, MW-3, and MW-4 were subsequently abandoned and MW2H was renamed as MW-2.

In 2016, borings for monitoring wells MW-PZ-U-1, MW-PZ-U-2, MW-PZ-U-3, MW-PZ-U-4, MW-PZ-U-5 and deep piezometers MW-PZ-L-1, MW-PZ-L-2, MW-PZ-L-3, MW-PZ-L-4, MW-PZ-L-5 were completed. Borings for

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monitoring wells MW-SA-1, MW-SA-4, and MW-SA-5 were completed in 2017. Logs of borings completed at JRPS between 1989 and 2017 are provided in Appendix C.

In general, the UWL is immediately underlain by clay and silty clay residuum, presumably deposited from erosion of the stream terrace to the north and west. Areas along James River are underlain by silty clay alluvium mantling sandy gravel alluvial material. Sandy gravel also appears to have extensively filled the shallow karst voids encountered in the relatively thin Burlington-Keokuk Limestone underlying the site.

Anderson Engineering, Inc. (AE) conducted a geotechnical investigation of the JRPS UWL in September 2018 for the purpose of analyzing stability of existing completed slopes at the landfill and slope stability analyses of the complete buildout of the landfill to the final permitted contours allowed under permit no. 707705 issued by the Solid Waste Management Program of the Missouri Department of Natural Resources (MDNR).

The investigation involved review of prior geotechnical work, site reconnaissance, geotechnical borings and sampling of CCR fill and soil, standard penetration tests, laboratory testing to determine geotechnical properties, and stability analyses.

AE site reconnaissance found no significant signs of instability and no significant evidence of erosion, which confirmed and supplemented earlier site reconnaissance conducted by GeoEngineers. AE slope stability analyses yielded critical factors of safety of 1.6 to 1.7 for both existing conditions and future buildout. A shallow surface sliding slope stability analysis was also performed for the landfill cover material and yielded a critical factor of safety of 2.0 for sliding failures. The AE report is included in Appendix D.

Based on the body of work completed at the site and performance of existing structures over a number of years, GeoEngineers assesses total settlement and differential settlement at the site to be insignificant.

10.0 FINDINGS AND CONCLUSIONS

Following are findings and conclusions resulting from the landfill stability demonstration:

1. Recognized and generally accepted good engineering practices were incorporated into the design of the CCR landfill to promote stormwater runoff, minimize changes in moisture content within the foundation materials, and provide for effective flood protection - which help ensure that the integrity of the structural components of the CCR landfill will not be disrupted. 2. The JRPS CCR landfill has operated for thirty years with no evidence of instability. 3. Drilling data shows karst voids beneath the site to generally be filled with alluvial sands and gravels. 4. Based on state of the art ERT and MASW investigations and analysis, there is no indication of any air- filled voids in the foundation materials or CCR materials which would suggest formation of cover collapse sinkholes beneath the CCR landfill. 5. Geotechnical analyses performed by Anderson Engineering, Inc. found the JTEC landfill to meet generally accepted standards for slope stability.

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6. GeoEngineers’ review of engineering properties of foundation materials and long-term performance of structures found that total settlement and differential settlement are insignificant with respect to landfill stability.

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12.0 REFERENCES

Anderson Engineering, Inc. 2018. Geotechnical Investigation Report, Assignment #7 – Slope Stability Study, Utility Waste Landfill, James River Power Station (JRPS), Permit #0707705.

Nuccitelli, S.A., 1991. Engineering Report for City Utilities, City of Springfield, Utility Waste Landfill, Springfield, Missouri.

Salvati, R. & Sasowsky, I.DD, 2002. Development of Collapse sinkholes in areas of groundwater discharge. Journal of Hydrology, 264. 1-11.

Tharp, T.M., 1999. Mechanics of upward propagation of cover collapse sinkholes. Engineering Geology 52, 13–33.

Waltham, T., Bell, F. G., & Culshaw, M. G., 2005. Sinkholes and subsidence: Karst and Cavernous Rocks in Engineering and Construction.

White, W.B., White, E.L., 1995. Thresholds for soil transport and the long-term stability of sinkholes. In: Beck, B.F., Pearson, F.M. (Eds.), Karst geohazards: engineering and environmental problems in karst terrane, Balkema, Rotterdam, pp. 73–78.

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FIGURES UTILITY WASTE LANDFILL AREA

µ 2,000 0 2,000

Feet

Vicinity Map Notes: 1. The locations of all features shown are approximate. 2. This drawing is for information purposes. It is intended to assist in City Utilities of Springfield - James River Power Station showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master Springfield, Greene County, Missouri file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Data Source: Mapbox Open Street Map, 2015 Figure 1 Projection: NAD 1983 UTM Zone 15N W:\Projects\15\15723009\GIS\Task 200 - Site Information Review\Figure 1 - JRPS Vicinity Map.mxd Date Exported: 02/16/16 by emayle 02/16/16 Exported: by Date Map.mxd Vicinity JRPS 1Review\Figure- SiteInformation - 200 W:\Projects\15\15723009\GIS\Task P:\15\15723009\GIS\MXDPDFDataJRPS\SiteDiagram_JRPS.mxd Date Exported: 10/17/18 by jbrown µ

Legend Scale 1:12,000 Site Boundary 1,000 0 1,000

Feet

Site Diagram

Notes: 1. The locations of all features shown are approximate. City Utilities of Springfield - James River Power Station 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached Greene County, Missouri document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Data Source: Aerial NAIP 2016 Figure 2 Projection: NAD 1983 UTM Zone 15N ELEVATION FT AMSL ELEVATION 1150 FT AMSL

1146 Alluvium 1128

Approx. Approx. Water Level b b b b b Water Level 1114 Burlington-Keokuk 1114

1100 1100

Elsey/ Reeds Spring

992 992 Pierson 978 978 Northview

Stratigraphic Units - Nuccitelli Monitoring Wells Notes: MW-1, MW-3, and MW-4 1. The locations of all features shown are approximate. 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached City Utilities - James River Power Station document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file Greene County, Missouri is stored by GeoEngineers, Inc. and will serve as the official record of this communication. 3. Nuccitelli reports estimate elevation to approximately one foot. All deep borings for the JRPS site ended in the Figure 3 Northview Shale formation. W:\Projects\15\15723009\GIS\MXDPDFDataJRPS\1572300900_NewVersionStratigraphicColumn.mxd Date Exported: 08/29/17 by emayle emayle by 08/29/17 Exported: Date W:\Projects\15\15723009\GIS\MXDPDFDataJRPS\1572300900_NewVersionStratigraphicColumn.mxd P:\15\15723009\GIS\JRPS Stability Report\JRPS Area Surface Geology.mxd Date Exported: 10/08/18 by jbrown

Mbk

Qal

Mbk

Legend Scale 1:12,000 1,000 0 1,000 Faults Qal - Quaternary Alluvium Feet Mbk - Mississippian Burlington-Keokuk Limestone µ

Surface Geology

Notes: City Utilities of Springfield - James River Power Station 1. The locations of all features shown are approximate. 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached Greene County, Missouri document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Data Source: Kenneth Thomson, ESRI, USDA NRCS Figure 4 Projection: NAD83 Missouri Central ft P:\15\15723009\GIS\JRPS Stability Report\JRPS Karst Map.mxd Date Exported: 09/21/18 by jbrown µ

Siphon Springs ` Cave ` Siphon Springs Cave Second Entrance

Qal

Legend Map Scale = 1:12,000 ` Caves E Springs 400 0 400

Sinkholes (GeoStrat) Feet Alluvium (Qal)

JRPS Karst Feature Map

Notes: 1. The locations of all features shown are approximate. City Utilities of Springfield - James River Power Station 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached Greene County, Missouri document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Data Source: Google Earth 2017 Aerial, Google Earth 1990 Aerial Figure 5 Projection: NAD 1983 UTM Zone 15N P:\15\15723009\GIS\JRPS Stability Report\JRPS Development.mxd Date Exported: 10/08/18 by jbrown µ

Legend Map Scale = 1:3,000 Phase I Toe of Slope Current Toe of Slope 400 0 400

Phase I Pond Feet Landfill Cap (Approx.)

JRPS Landfill Development

Notes: 1. The locations of all features shown are approximate. City Utilities of Springfield - James River Power Station 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached Greene County, Missouri document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Data Source: Google Earth 2017 Aerial, Google Earth 1990 Aerial Figure 6 Projection: NAD 1983 UTM Zone 15N P:\15\15723009\GIS\JRPS Stability Report\Figure 7 - JRPS ERT and MASW.mxd Date Exported: 10/17/18 by jbrown

µ 400 401 402 403 404 405 406 407 408 409 410 411 412 413

415 416 E 417 418

420 421 422 423 424 425 426 427 E 428 E 429 431 432 433 434 435 436 437 438 E 439 440 E 441 442 443 444 445 446 447 448 449 450 E 450 E 451 451 452 453 454 455 455 456 456 457 458 459 460 E E E 461 E 462 463 464 465 466 467 468 469 470 470 471 E 472 E E E 472 473 474

535 475 476 477 478 479 480

536 481

533 482 483 E E E 484 485 486 487 487 488 489 489 490 491 492 493 494 E E E E 495 496 496 497 498 499 499 500 500 501 535 536 502 503 504 504 505 E E 506 506 507 508 508 509 509 510 511 512 512 513 513 514 515 516 516 EE 517 518 519 520 521 522 523 523 524 525 Cultural 526 527 Resource 528 528 Site 537 538

Legend 500 0 500 ERT Lines Feet Cultural Resource Site E MASW Sounding Centerpoint

ERT And MASW Locations

Notes: 1. The locations of all features shown are approximate. James River Power Station UWL 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file Springfield, Greene County, Missouri is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Data Source: Figure 7 Projection: NAD 1983 UTM Zone 15N Not to Scale

Ground Surface Elevations

City Utilities of Springfield – James River Power Station Notes: 1. The locations of all features shown are approximate. Greene County, Missouri 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by Figure 8 GeoEngineers, Inc. and will serve as the official record of this communication. µ

Top of Rock Elevations

Notes: City Utilities - James River Power Station 1. The locations of all features shown are approximate. 2. This drawing is for information purposes. It is intended to Greene County, Missouri assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the Figure 9 official record of this communication. W:\Projects\15\15723009\GIS\MXDPDFDataJRPS\StabilityRptF6_TORElevation.mxd Date Exported: 08/22/17 by emayle emayle by 08/22/17 Exported: Date W:\Projects\15\15723009\GIS\MXDPDFDataJRPS\StabilityRptF6_TORElevation.mxd µ

Combined Soil and CCR Thickness

Notes: City Utilities - James River Power Station 1. The locations of all features shown are approximate. 2. This drawing is for information purposes. It is intended to Greene County, Missouri assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the Figure 10 official record of this communication. W:\Projects\15\15723009\GIS\MXDPDFDataJRPS\StabilityRptF7_SoilAshThickness.mxd Date Exported: 08/22/17 by emayle emayle by Exported: Date 08/22/17 W:\Projects\15\15723009\GIS\MXDPDFDataJRPS\StabilityRptF7_SoilAshThickness.mxd P:\15\15723009\GIS\JRPS Stability Report\Figure 11 - JRPS Interpreted Joint Trends.mxd Date Exported: 10/17/18 by jbrown

µ 400 401 402 403 404 405 406 407 408 409 410 411 412 413

415 416 417 418

420 421 422 423 424 425 426 427 428 429

431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 450 451 451 452 453 454 455 455 456 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 470 471 472 472 473 474

535 475 476 477 478 479 480

536 481

533 482 483 484 485 486 487 487 488 489 489 490 491 492 493 494 495 496 496 497 498 499 499 500 500 501 535 536 502 503 504 504 505 506 506 507 508 508 509 509 510 511 512 512 513 513 514 515 516 516 517 518 519 520 521 522 523 523 524 525 Cultural 526 527 Resource 528 528 Site 537 538

Legend Scale 1:3,000 400 0 400 ERT Lines Feet Cultural Resource Site Interpreted Joint Trends

Interpreted Joint Trend Locations

401 MW4 _ 103 B& !P _ PZ-SA-L-1 102 _

105 104 _ _ 402 PZ-SA-U-1 _ A@ 301 )"

106 108 107 _ _ _

201 _ 237 _

203 _ 202 MW-SA-4 _ A@ 109 _ 302 110 )" 236 _ _ 111 238 _ 204 205 _ _ _ 314 _206 )" 112 PZ-SA-L-5 _ !P A@PZ-SA-U-5

207 208 239 _209 303 _ _ _ )" PZ-SA-L-2 403 !P_ 230 _ 304 PZ-SA-U-2A@B& )" MW1 MW3 113 B& 114 _ 210 315 211 317 _ _ _ )" _ _ _235 )" 240 212 115 116 _ 305 241 _ )" _

234 213 214 215 _ _ _ _ 231 _ 121 MW-SA-5 _ A@ 306 216 217 218 )" _ _ _ 242 119 118 307 _ _ _ )" 316 )" _ A 232A@ _ 120 B 220 C 221 _ PZ-SA-U-3_ 219 _ _ _ _ D E _ _ 308 PZ-SA-L-4 A@ )" F !P _ 309 PZ-SA-U-4 )" 222 223 224 _ _ _ _233

PZ-SA-L-3 !P 225 @ 227 _MW-2 _ _ AG 226_H_J MW2 _ B& 310 _K )"

228 _ 229 311 _ _ )"

)" Legend Map Scale = 1:3,000 _ Historical Geotechnical Borings 400 0 400 )" Historical Test Pits B& Historical Monitoring Wells (Abandoned) Feet A@ Current Monitoring Wells !P Current Piezometers JRPS Boring Location Map

Notes: 1. The locations of all features shown are approximate. City Utilities of Springfield - James River Power Station 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached Greene County, Missouri document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Data Source: Google Earth 2017 Aerial, Google Earth 1990 Aerial Figure 12 Projection: NAD 1983 UTM Zone 15N